MULTIPLE STANDARD ADDITION WITH LATENT-VARIABLES (MSALV) - APPLICATION TO THE DETERMINATION OF COPPER IN WINE BY USING DIFFERENTIAL-PULSE ANODIC-STRIPPING VOLTAMMETRY

MSALV, multiple standard addition with latent variables, is a new meth od designed to overcome the difficulties presented by the determinatio n of an analyte in a complex sample in which equilibria exist whose di splacement may alter the response of the sensors when the analyte is a dded in a multiple addition. MSALV has been used to quantify the Cu co ntent in samples of wine using differential-pulse anodic stripping vol tammetry (DPASV) with a mercury electrode and ethylenediaminetetraacet ic acid (EDTA) and KCl as complexing agents. The existence of the EDTA -Cu(II) complex and Cu(I)-chloride complex intermediate leads to a cha nge in the sensibility of the sensors when Cu(II) is added, which must be born in mind during construction of the multiple addition model. T he use of latent variables calculated by partial least squares (PLS) p rovides a solution which is both quantitatively adequate and chemicall y interpretable. The results of four repeated determinations of Cu in samples of red wine are shown. In each case the latent variables were calculated from the intensities recorded at fifteen potentials in eigh t voltammograms corresponding to the successive additions of wine and/ or copper.